Developmental Variation in Monosialoganglioside Content of Embryonic Chick Retina and Tectum

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Abstract
Monosialogangliosides were extracted from the retinas and optic tecta of chick embryos at 6–12 days of incubation, and analyzed by high-performance liquid chromatography. The dominant monosialoganglioside was found to be N-acetyl-galactosaminyl (N-acetylneuraminyl) galactosylglucosylceramide (GM2). The specific concentration of GM2 in both the retina and tectum rose to a peak at 8–9 days of incubation, then declined. At day 10, GM2 was significantly lower in the dorsal than in the ventral or temporal quadrants of the retina. The same trend to a lesser degree was seen in the tectum. These results demonstrate striking variations in the monosialoganglioside content of the retina and tectum during formation of the retinotectal projection, and suggest that topological gradients may be a consequence of these developmental and spatial variations.